(A) Field of the Invention:
The invention relates to improvements in beverage brewing machines. More specifically, the invention relates to a beverage brewing machine which permits the brewing of a larger cup of beverage without affecting the quality of the beverage.
(B) Prior Art:
The present invention is an improvement in beverage brewing machines of the type taught in my U.S. Pat. No. 3,565,641, issued Feb. 23, 1971. The patent teaches a beverage brewing vending machine for brewing a single cup of beverage which has a brewing chamber for receiving hot water and beverage material. The chamber has a floor permeable to gas and liquid and impermeable to the beverage material. The apparatus includes a second or lower chamber of substantially the same or smaller cross-sectional size and located below the first chamber with a piston therein. Movement of the piston toward the floor of the first chamber forces air through the floor into the first chamber to agitate and brew the hot water and beverage material mixture to produce the beverage. Movement of the piston away from the floor withdraws the beverage through the floor to dispense it. The size of the cup of beverage which can be brewed with this machine is determined by the size of the second or lower chamber of the machine. Thus, in order to increase the size of the cup of beverage brewed, it would be necessary to increase the size of the second chamber. This can be done either by increasing the length or diameter of the second chamber.
Increasing the length of the chamber does not provide the optimum solution as it takes a substantial increase in length to produce an increase in volume, as the change in volume is linearly related to the change in length. As lengthening the second chamber requires also increasing the machine size, this solution is undesirable.
When the diameter of the chamber is increased, a change in volume is proportional to the square of the change in diameter. Thus a relatively smaller change in diameter can result in a larger change in volume. Accordingly, it is preferable, from a size-point-of-view, to increase the diameter rather than the length of the lower chamber.
However, increasing the diameter of the chamber also increases the diameter at the top opening thereof. As a result, the ground beverage material disposed on the filter-floor of the brewing chamber, which also covers the top opening of the lower chamber, is spread over a larger filter area so that a thinner "patty" of a given amount of material is formed. Under these conditions, a poorer quality of beverage is brewed and more filter paper is used.